Storms from Outer Space

Storms from Outer Space

Article excerpt

It's not easy being human: some things are just too impressive to appreciate. Take the storm that is raging on Saturn, for example. It covers an area the size of the earth. How do you begin to wrap your imagination around that?

Then there's the fact we have finally worked out what creates such a monster, and why these storms arise only every few decades. For this, a phenomenon that occurs more than a billion kilometres away, we now know a truly impressive amount. A paper published this month in the journal Nature explains the detail for the first time. All the data we have gathered tells us that Saturn's storms--also known as its Great White Spots --are uncannily like terrestrial thunderstorms. They arise from a scaled-up and twisted version of our own water cycle, complete with spectacular lightning discharges.

The difference between earth's and Saturn's storms lies mainly in the composition of the atmosphere. Saturn is coated in a layer of hydrogen and helium, the two lightest gases. Water vapour is much heavier. Consequently, the process of heating and convection that drives an almost daily cycle of cloud build-up and discharge on earth takes about 20 years on Saturn.

Water is also involved in another impressive new discovery--this time on Mars. In March, observers using Hawaii's Keck and Infrared telescopes revealed that the atmosphere of Mars still holds traces of a huge lost ocean. The 20 million cubic kilometres of water would have been roughly a mile deep in places and covered a fifth of the Red Planet's surface. Though dry and dusty now, Mars might once have been extremely hospitable to life.

What's more, there may be enough water left on or under the planet's surface to keep some life forms going. Nasa's Curiosity rover has been measuring how temperature and humidity rise and fall there through the day and night. …